Drawing press



Nov. 26, 1940. H. F. M MlLLlN DRAWfNG PRESS Filed Oct. 17, 1938 2 Sheets-Sheet 2 Jwm Howmo EMnc MILLIN,

Patented Nov. 26, 1940 UNITED "STATES 2,222,851 DRAWING rnnss Howard F. Mount Gilead, Ohio, assignor to- The Hydraulic Development Corp.

Inc., Wilmington, Del.

ware v t Application October 17,

' 3 Claims.

This invention relates to drawing presses, and in particular, to such presses having blank holders for holding .the margins of the workpiecev during operations by the drawing plunger. One. object of this invention is to provide a drawing press having a main platen for holding the drawing die, and a blank holder platenlocated on the opposite side of the main platen from the workpiece and engaging the workpiece 10 by members-passing through the main platen.

Another object is to provide such a drawing press, whereina plurality of work-holding inemhers is provided for use wtih a single blank holder platen in order to adapt the drawing press to various sizes and shapes of drawing dies and workpieces.

Another object is to provide a drawing presshaving a main platen and a blank holder platen on the opposite side of the main platen from the workpiece, with means for generating pressure fluid to operate the blank holder platen in response to the motion of the main platen.

Another object is to provide such a drawin press as set forth in the preceding paragraph ti 25 wherein the blank holder rams for operating th blank holder platen are arranged so that the pressure generation, due to the motion of the main platen, acts in a direction assisting ther main platen, jand withoutany substantial op- 80 posing force.

c In the drawings: a

Figure 1 is a diagrammatic view in central vertical section through the principal operating elements of a di'awing press [according tolthe present invention, with a suitable operating circuit. c v 7 Figure 2 is across section along the line 2-2 in Figure l. a

- Figure 3 is a front elevation of a commercial form of drawing press embodying the invention of Figures 1 and 2.

Figure-l is a cross section along the line 4-4 in-Figure 3. v8 i General arrangement I In general, the drawing pr ess of this invention consists of a bedior supporting the ho low die, 7 a main plunger ,and platen for supporting and moving the punch or forming die, and a blank" 50 holder platen disposed on theopposite sideof the main platenirom the workpiece. Provision is made for plungers to. operate the blank'holder platen by means of pressure generated inv response to the'motion of the main platen, anddn 55 such manner that the. operation oi-the blank vide a blank holder platen which is stiff enough made as heavy and as rigid as desired without requiring any additional blank holder platens. In-

stead, a number of comparatively light-weight t a corporation ot Dela- C J 1938,"Serial No. 235,316 I holder plungers does not subtract anysubstantial amount of force from the operation of the main plunger and main platen. The workpiece blank is held in position on the hollow .die (lyre ing the drawing operation by a hold-down we which is connected to the blank holder platefiby .means of rods running through holes in the main platen. If the drawingpress is a vertical form of press, as shown in the drawings, then the blank holder platen according to-the present 10 invention is located above the main platen for a downwardly-acting main plunger and "main platen. F c c Hitherto, where drawing presses have been provided with blank holder platens beneath the main platen and directly in contact with the workpiece, it has been necessary to cut an aperture in the blank holder platen closely corret sponding with the size and shape of the drawing die or punch. Thus,if a variety of workpieces of 20.

widely 'varying sizes or shapes was to be drawn on the same press, it was necessary to change blank holder platens in order that the new punch and? blank holder platenwould correspond closely in size and shape. It has also been necessary to pro-' :to resist bending stresses, hence, the necessityior providing a number of blank holder platens in order to accommodate the press to varying sizes and shapes of workpieces, resulting in very expen sive equipment and the limitation of flexibility of such equipment for workpieces. r O

Accordingto the present invention, by placing the blank holder on the opposite side of the main, platen from the workpiece, only one blank holder platen is required for all jobs withinthe capacity of the press, and this blank holder platen can be producing varying shapes of and relatively inexpensive hold-down plates for holding the workpiece are provided of a variety of shapes and sizes to suit corresponding workpieces. Thesehold-down Plates are connected to the blank holder platen by means of rods passing through holes in the main platen and the latter can be drilled with numerous holes in order to render it adaptable to all varieties of workpieces. The pressure-applying mechanism employed with the press of the present invention is 7 likewise adaptable to exertingdifierent pressures at difierent portions of the'workpiece, according to the requirements of the particular job. I)

Construction Referring tothe drawings in detail, Figure 1 shows diagrammatically the principal working elements of a drawing press according to the present invention, together with a suitable operating circuit. The press of Figure 1 consists of a bed l0 and a head II, the strain rods and other usual frame members being omitted to clarify the disclosure. Mounted upon the bed [0 is the hollow die l2 with the workpiece l3 supported thereon, and having a die cavity 14 for receiving the drawing die or punch 15. The latter is mounted uponithe main platen-l6, which in turn, is connected to the main plunger' l1 having a piston head [8 reciprocable within the cylinder bore IQ of the main cylinder 26 mounted on the press head H. A packing 2i and gland 22 prevent leakage around the main plunger l1, and ports 23 and 24 serve for the distribution of fluid to the .main. cylinder bore I9.

The press head II is provided with blank holder balancing cylinders 25 having bores 26 into which the hollow blank holder plungers 21 are reciprocable, leakage being prevented by the packings 28 and glands 2a. The cylinder bores 26 are provided with intake ports 38 and discharge ports 3| and .32. The blank holder plungers 21 are secured to the blank holder platen 33 by'means of the split rings 34 operating in grooves 35, and extend downwardly into cylinder bores 36 within the main platen l6, leakage being prevented by the packlngs 31 and glands 38. The blank holder platen 33 is likewise provided with an aperture 38 for the passage of the main plunger l1 and carries rods 46 extending through holes 4| in the main platen Hi, the rods 46 being secured at their lower ends to the hold-down plate 42 having an aperture 43 for the passage of the drawing die or punch l5.

The blank holder plungers 21 are provided with heads 44 reciprocable in the bores 36, and also with l .-shaped passages 45 running from adjacent the heads 44 to the opposite ends of the blank holder plungers 21, and there opening into the cylinder bores 26 in the blank holder balancing cylinders 25. The cylinder bores 36 are provided at their lower ends with leakage vanes 46, which provide for drainage of fluid leaking past the blank holder plunger heads 44, these vanes 46 being preferably connected by piping (not shown) back to the fluid tank 41 mounted on the press head II. In practice, it 55.will be understood that the shapes and sizes oi the dies l4 and I5 will vary according to the workpiece to be produced, thereby varying the shape of the aperture 43 in the hold-down plates 42. A variety of hold-down plates 42 can be provided, however, and connected to the blank holder platen 33 by the rods 46. h

, Press-operating circuit The drawing press of this invention may be operated by a number of hydraulic circuits, that shown in Figure 1 being suitable for applyingdiiferent'pressures at difierent points on the periphery of the-workpiece l3. In the circuit shown in Figure 1 there isprovided fluid presv 7o'sure pump 48, having a suction line 48 running back to the tank 41 and a.discharge line 58 running to the main control valve 51, the;latter' being a four-way valve for reversing the flea of the pump"; re atively to the main cylinder 26,

not under pressure to the tank 41 by means of the exhaust line 52. From the main control valve 5| the lines 53 and 54 run to the ports 23 and 24 in the main cylinder bore l5.

Each .blank holder balancing cylinder 25 is provided with a suction line 55 connected to the port 30, and terminating in a check valve 56 opening toward the port 38; The cylinders 25 are also provided with exhaust lines 51 passing through-check valves 58 opening in adirection away from the ports 3| and uniting in'the line 58 connected to the two-way platen-operated valve 66.

operated by a valve rod 62 by means of a cam 63, engaged and shifted by a platen arm 64 extending outwardly from the main platen l6. Connected to the ports 32 in the blank holder cylinders 25 are additional discharge lines 65 having pressure gauges '66 associated therewith Operation In the operation of the drawing press shown in Figures 1 and 2, the pump 48 isstartcd and 42, which is suspended from the rods 48. Pressure is then supplied to themain ram area above the piston head 18 by shifting the main control valve 5|, so that the pump 48 discharges pressure through the lines 58 and'53, the line 54 opening into the space beneath the main plun er head I 8 being connected to the exhaust line 52. It will be understood that the usual surge valve system may also be applied to the main cylinder 20 to assist and accelerate the gravitational descent of the main plunger [1, as is well known tothose skilled in the hydraulics art, but this system has been omitted to simplify the disclosure.

The latter is provided with an exhaust line 61 extending into the tank 41 and is i the workpiece blank 13 is placed on top of the -hollow die l2 and beneath the hold-down plate Under these circumstances the main plunger 11, main platenv l6 and drawing die or punch l5 descend. The blank holder platen 33 likewise descends and the blank holder plungers 21 draw oil or other operating fluid into the blank holder cylinders 25, through the check valves 56 and lines 55. By the timethe hold-down plate 42 reaches the workpiece blank l3 the platen arm 64 has engaged and shifted the cam and valve rod 62 downwardly, closing the normally open two way valve 68. After this occurs fluid can-'- notescape through the lines 51 and 53 and the check valves 58. Upon engaging the workpiece blank I3 the hold-down plate 42 halts, and consequently halts the blank holder platen '33 through the rods 40 connected thereto. The main platen l6, however, continues to move downward, hence, the cylinder-bores 36 are pulled downwardly away from the blank holder plunger'heads 44. Fluid in the cylinder bores 36 above the heads *44 cannot escape except through the plunger passageways 45, into the blank holder balancing cyl-.

inders 25. From these cylinders it cannot escape at the me time connecting the line wh ch is except through the pressure relief valves 61 or 7 continues to move downwardly, and by its mot'ion generates fluid pressure within its cylinder bores 36.

- blank holder balancing cylinders 25 reaches the setting of its respective relief valve 61, the latter opens and discharges into the exhaust line 68 all fluid in excess of its set pressure, the discharged fluid escaping to the tank 41. The pressure thus generated within the blank holder balancing cylinders 25 acts upon the annular piston areas 10 upon the upper ends thereof, so as to urge the blank holder plungers 21 and blank holder platen '33 downwardly, thereby applying pressure through the rods 49 to. the hold-down plate 42, and holding the workpiece blank I3 against the hollow 'die l2; It will be observed thatin this arrangement the pressure generated within the main platen cylinder bores 35 urges the blank holder plunger 21 downwardly so that the only force'th'at is subtracted from the force exerted by the main plunger "is that due to the pressure acting upon the annular areas immediately above the blank holder plunger heads 44, and constituting diiierential areas representing the diiierence between the press sectional areas of the plungers 21 and their heads 44. v

i As the main platen l6 continues to move downw'ardly, the punch or drawing die l engages the workpiece blank l3 .and forces its central portion- 35 4 time, however,-the blank I3 is allowed to slip downwardly into the die cavity l4. At the same inwardly at its edges because the pressure upon the hold-down plate 42 is so adjusted, by means of the pressure relief valves 61, as to permit the proper amount of slippage in the blank 13 during the drawing operation. When the main platen l6 and drawing die l5 have moved the proper distance, or have exerted the desired pressure, the main control valve 5| is shifted so as to connect the pump pressure line with the pull-back line 54 while connecting the pressing line 53 with the exhaust line 52. Pressure fluid is then exerted J against the under side of the mainplunger'head small amount at first because of the fluid trapped in the blank holder balancing cylinders 25. slight amount of motion may occur, however, due,

heads 44, thereby creating a slight void l8, causing the main plunger I1 and main platen Hi to rise on their retraction strokes. The blank holder platen 33, however, moves a relatively to the slight withdrawal of fluid from the cylinders 25through the passages 45 into the main' platen-cylinderbores 36, as the latter move upwardly with relation to the blank holder plunger in the cylinder bores 36. J

Because of the weight of the blank holder platen 33, blank holdergplungers 21, r'ods 40 and hold-down plate 42, however, the latter will re-* maintemporarily resting against the blank l3 during therflrst part of the retraction stroke of the workpiece from the drawing die or punch l5, after which the platen arm 64 rising releases. the cam 63 and valve rod-62 so as to permit the opening of the normally open two-way valve 60, thereby permitting the fluid in the; blank holder cylinders 25to exhaust through the lines 51, 59and-6I and the check valves 58 and two-way valve 60.-

. v ,platen l6. The check valves 58 prevent equaliza- When the pressure .thus generated within the tion of the pressure in the .several'blank holder cylinders 25 during the blank-holdingoperation. thereby permitting difierent blank-holding pressures to be exerted by dliierentblank-holding .the press head13 is a electric motor 80.

plungers 21. It will be obvious, however, that the check valves 58 maybe omitted and the same- -blank-holding pressures thereby applied to all of the blank-holding plungers21 if the user so desires. In the latter arrangement a single pressure relief valve 61 could be used to exert the single blank-holding pressure.

Commercial form of press The press of Figures 1 and 2 is illustrated indiagrammatic form. Figures 3 and 4, however, show a press having the blank-holding platen above the main platenand embodying the features of the invention in'commercial form. This and a head -13, interconnected by strain rods .14 terminating-in. the nuts 15 threaded upon the ends thereof. The press head'13 carries a main cylinder 16 and a tank 11, together with the blank so 25,. commercial form of press consists of a bed 12 holder .cylinders 18, similar to the blank holder cylinders previously described. Mounted upon pump 19 operated by an The blank holder cylinders 19 contain hollow blank holdemplu'ngers 8| intermediately connected to the blank holder platen 92, and at their lower ends passing into pressure-generating cylgtepding into the main cylinder", in a manner ,similar to that shown and described in connection with Figure 1. In Figures 3 and 4,.however, the punch and hollow die have been omitted because the shapes and sizesof these, members vary according to the particular kind of workpiece to be produced, The main'platen 84 carries a platen arm88 arranged to engage a collar 89 upon thecontrol rod 90, reciprocably supported in the brackets 9| and 92. By-way of variation, however, the pump 19 is of the reversible variable delivery type having a and cqntrolled' by the control rod 90 through suitable mechanism. The control rod 90'may .alsqbe operatedmanually by means of the hand lever 94, mounted .-as at,95, upon thepress bed I come within the I claim as new and I holder-operating cylindu', a main plunger recontrol member 93 operating a'servomotor, in a manner well known to those skilled in the art,

It will be understood that I desire to coinprehend within my invention such modifications as" invention. l

- Having thus fully'described m'yinventionwhat 7 desire to secure by Letters Patent,is:

' 1. In a drawing a press head having a maincylinder and a blankscope of the claims, and the press, a work support, a name,

'ciprocable in saidcmain cylinder, a hollow blank holder plunger reeiprocable in said blank-holderplunger head whereby relative movement between said cylinder and head will generate .fluid pressure, a blank holder platen connected to said blank holder plunger and located between said main platen and press head,- a work-holding member mounted on the opposite side'of said main platen from said blank holder platen, and a connecting element extending between said work-holding member and said blank holder platen, said work-holding member being adapted to be disconnected from the blank holder platen for replacement by another work-holding member;

, 2. In a drawing press, a work support, a frame, a press head having a main cylinder and a blankholder-operating cylinder, a main plunger reciprocable in said main cylinder, a hollow blank holder plunger reciprocable in said blank-holderoperating cylinder and having a head thereon, a main platen connected to said main plunger and having a cylinder for receiving said blank holder plunger head whereby relative movement between said cylinder and head will generate fluid pressure, a blank'holder platen connected to said blank holder plunger and located between said main platen and press head, a work-holding member mounted on the opposite side of said main platen from said blank holder platen, and detachably connected with .said blank holder platen by a connecting element extending between said work-holding member and said blank holder platen, and means responsive to the attainment of a predetermined pressure in said blank-holder-operating cylinder for releasing fluid therefrom.

3. In a drawing press, a work support, a frame, a press head having a main cylinder and a blank-holder-operating cylinder, amain plunger reciprocable in said main cylinder, a hollow blank holder plunger reciprocable in said blankholder-operating cylinder and having a head thereon, a main platen connected to said main plunger and having a cylinder for receiving said blank holder plunger head whereby relative movement between said cylinder and head will generate fluid pressure, a blank holder platen connected to said blank holder plunger and located between said main plate, and press head, a movable work-holding member mounted on the opposite side of said main platen, said work-holding member being detachably connected with said blank holder platen by a connecting element extending through said main platen, means responsive to the attainment of a predetermined pressure in said blank-holder-operating cylinder for releasing fluid therefrom, a tank, a conduit interconnecting said fluid-releasing means with said tank, and a valve in said conduit closable in response to a predetermined travel of said main platen for preventing release of fluid through said conduit.

. HOWARD F. 

